The present invention relates to a laser/MIG hybrid welding process using high wire speeds.
When it is desired to weld one tube or pipe to another (butt welding) or else to manufacture a tube or pipe by longitudinally welding the two longitudinal edges of a metal sheet shaped beforehand into a “U” and then an “O”, bevels are generally provided on the edges to be welded together, typically forming a groove in the shape of a “V”, an “X” or other shape.
If it is desired to fill this bevel by depositing metal therein by carrying out a laser/MIG (Metal Inert Gas) hybrid welding process, a diagram showing the principle of which is given in FIG. 1, it is necessary to achieve high welding rates, that is to say rates of at least a few m/min, so as to maintain the productivity of the process.
Now, the higher the welding rate, the higher the wire feed rate has to be, so as to be able to rapidly fill the volume of the bevel, that is to say “V”-shaped, “X”-shaped or other shaped groove, at the welding speed in question.
Under these conditions, as soon as welding rates of around 2 m/min or higher are reached, this results, typically for thicknesses of 8 mm and taking into account the bevel shapes adopted, in having to increase the feed speed of the wire beyond the limits usually encountered on wire feeders, namely typically around 20 m/min.
One solution for increasing the rate of deposition is therefore to increase the wire diameter, since the wires conventionally used have a diameter of 1.2 mm.
However, the problem that then arises is that, for a constant rate of metal deposited, a higher current is therefore needed to melt the high-diameter wires, that is to say those of around 1.6 mm in diameter, but in this case the process runs into the current limitation of most MIG generators, which is conventionally around 450 A, which limitation therefore does not allow currents greater than this value to be delivered.
The problem which then arises is how to be able to fill a bevel at high speed without encountering the abovementioned drawbacks and limitations.